General Science GK Questions with Answers – Page 110

Collenchyma cells lay down extra cellulose and pectin at the corners of their walls, which makes the tissue strong and yet flexible.

Papaya is raised from seed, so it is not multiplied by vegetative propagation the way the other three plants are.

Green plants give out oxygen only during photosynthesis, the process in which they use light energy to make their own food.

A body that slides down a smooth slope turns all of its potential energy mgh into translational kinetic energy and reaches the bottom with a speed equal to the square root of 2gh.

The force on a current carrying conductor kept in a magnetic field is given by F equal to B I L sin theta, where theta is the angle between the direction of the current and the direction of the field.

The law of conservation of linear momentum follows straight from Newton's second law: the rate of change of the momentum of a system equals the net external force acting on it, so when that force is zero the total momentum stays the same in size and in direction.

Dynamic viscosity measures how strongly a fluid resists flowing, and in the centimetre gram second system it is measured in poise, a unit named after the French physician Jean Louis Marie Poiseuille, who studied the flow of blood in narrow tubes.

In 1820 the Danish scientist Hans Christian Oersted saw that a compass needle kept near a wire swung aside the moment a current flowed through the wire, and swung the other way when the current was reversed.

Once the athlete's feet leave the ground they move as a projectile, and the horizontal distance covered, called the range, is given by R equal to u squared into sin 2 theta divided by g. The range is largest when sin 2 theta has its greatest value of one, which…

The loudness or intensity level of sound is measured in decibels (dB), a unit named after Alexander Graham Bell.

Bleaching powder, calcium oxychloride, is made in industry by passing chlorine gas over dry slaked lime, that is calcium hydroxide.

Tooth enamel is made of calcium phosphate, the hardest substance in the body, and it begins to corrode when the pH in the mouth drops below about 5.5.

A salt takes its character from the strength of the acid and the base that formed it. Ammonium chloride comes from hydrochloric acid, a strong acid, and ammonium hydroxide, a weak base, so the strong partner dominates and the solution has a pH below seven.

The stomach wall secretes hydrochloric acid, which makes the gastric juice strongly acidic, helps the enzyme pepsin digest proteins and kills many germs swallowed with food.

Plaster of Paris is calcium sulphate hemihydrate, made by heating gypsum, which is calcium sulphate dihydrate, to about 373 kelvin so that it loses three fourths of its water of crystallisation.

The sting of an ant and the hairs of the nettle plant inject formic acid, also called methanoic acid, which is why the skin burns; rubbing on a mild base such as baking soda or the leaf of the dock plant relieves it by neutralising the acid.

Baking soda is sodium hydrogen carbonate, a mild, non corrosive base used as an antacid, as an ingredient of baking powder along with a mild edible acid such as tartaric acid, and in soda acid fire extinguishers, where it releases carbon dioxide.

Borax, sodium tetraborate, is the salt of a strong base, sodium hydroxide, and a weak acid, boric acid, so its solution in water is basic.

The pH is the negative logarithm of the hydrogen ion concentration, so each rise of one unit means the concentration has fallen to one tenth.

Citrus fruits such as orange, lemon, lime and grapefruit owe their sharp sour taste to citric acid, which is the acid textbooks name for this family and the one examiners expect here.